Windfarms in General: Carbon efficiency

The Sustainable Development Commission, which is the Government's independent watchdog on sustainable development, write that the energy payback of wind farms has been estimated at 3--10 months. (click here to download the full document)

Dr J. R. Etherington writes in his document: "The Case Against Windfarms" under the heading 'Myths of our own making':

  • "It is often said that wind turbines fail to pay back the energy and CO2 cost of their manufacture and erection, or even that the CO2 emission from cement manufacture alone is enough to offset the lifetime saving of CO2 by a turbine. All of these assertions are untrue. Don't repeat them - there is enough to complain about in wind power without resorting to easily exposed misinformation but for more detail see Roads (below) and Payback time for energy and CO2 (section 5)."

So, if even the wind farm opposition agrees, we should conclude, that wind farms are carbon efficient!

One argument that I have come accross many times while being involved in writing this website is following:

  • wind blows very inconsistently -the average turbine produces only ~30% of its stated capacity)
  • as there are times of less or even no wind, there is a need to have conventional powerstations on standby to ensure steady supply of energy.

Windfarm opposition now often state that this 'energy on standby' would produce more CO2 than the amount saved by wind turbines.

It is very difficult to find reliable informations on this. So here what I found:

  • The Renewable Energy Foundation publishes data on the energy produced and their LoadFactor of the windfarms in the UK. (http://www.ref.org.uk/Pages/4/uk_renewable_energy_data.html)
    The Load Factors are in a range from 3% to 58% with an average of ~ 25-30% ?.
  • The best (and only) information I have found on the requirements of energy backup for wind generated power I have found at the website of the Tyndall Centre for Climate Change Research in their document : Security assessment of future electricity scenarios It is a very technical report, but from what I understand I can state following:
    • At lower levels of wind penetration the capacity credit of wind generation is found to be about the same as the average load factor of wind. (so each Watt of produced windenergy actually replaces one Watt of conventional power)
    • At higher levels of installed capacity this begins to tail off to about 50% of the installed capacity...
    • There is an interesting graph on Page 22 of above document. In short:
      They assume an energy requirement of 25GW:
      • a system with only conventional energy production would require an additional of backup energy.
      • a system with only wind energy would require an additional 20.5GW for backup, so replacing only 4.5GW of conventional energy.
    • To put these numbers into relation: The UK has about 2GW of installed Wind capacity, which equates to 4% of the domestic consumption (Source: BWEA UKWindsatus2007)
      This would equate to 50GW installed capacity and a (conventional) backup requirement of 14GW. I think the 2GW of wind capacity are easyly covered!!!

There is also an interesting document on this topic on the BWEA website: Blowing away the Myths